Mysterious Object Discovered Near Supermassive Black Hole

Astronomers using the Very Large Array (VLA) have
spotted a curious object orbiting Cygnus A, a famous supermassive black hole
and one of the strongest sources of radio waves in the universe.

The new discovery, accepted in the Astrophysical Journal,
is a bright object close to the galaxy core and was spotted when a new
emission of radio waves appeared. The culprit is either an extremely rare
example of a supernova or, more likely, a second supermassive black hole. If
the object is indeed another supermassive black hole, we might have missed the
whole picture of Cygnus A.

“This new object may have much to tell us about the
history of this galaxy. Further observations will help us resolve some of these
questions. In addition, if this is a secondary black hole, we may be able to
find others in similar galaxies.” lead author Daniel Perley, of the
Astrophysics Research Institute of Liverpool John Moores University, said in a statement.

The presence of a second black hole indicates that
Cygnus A experienced a collision with another galaxy in the recent cosmic past.
The object is only 1,500 light-years away from the central black hole, and if
its nature is confirmed, this would be the closest pair of supermassive
black holes ever discovered.

GIF showing the 1989 and 2015 observations of
Cygnus A.

The new object is under the right beam from the central black
hole.

Perley, et al., NRAO/AUI/NSF, NASA

More observations are necessary to actually confirm
what the object is. Until then, astronomers are looking for other explanations,
for example an incredibly powerful supernova. The supernova hypothesis is
unlikely because the source seems to be very bright and long-lasting, factors
that go against expected supernova behavior.

The object was detected in the latest observations
of Cygnus A, which is over 800 million light-years away. Being such an
incredibly bright object, Cygnus A has been observed many times by many
instruments since it was discovered in 1939. It was also an early target for
the VLA when it opened in the 1980s and it has been observed again in 1996.
Only one radio source, the central supermassive black hole, was ever seen.

The region was also observed both by Hubble and the
Keck observatory, which considered it a dense agglomeration of stars. It’s only
in the latest observation campaign from 2015/2016 that the new source appears.
If it’s a black hole, it means that it’s feeding.

“To our surprise, we found a prominent new feature
near the galaxy’s nucleus that did not appear in any previous published images.
That means it must have turned on sometime between 1996 and now.” Rick Perley
from the National Radio Astronomy Observatory added.

Soon enough, the mystery of the Cygnus A’s companion
won’t be much of a mystery.